The present invention relates to an improvement in the manner in which the rear suspension of a typical snowmobile is constructed. More specifically, to a method of varying the vertical force that is necessary to compress the spring component of the rear suspension. This has the effect of stiffening the ride at the rear of the snowmobile which improves its handling and performance characteristics under certain riding conditions and is especially advantageous for use in snowmobiles that are used for racing.
It has long been known by motor sports enthusiasts that a key to improving the handling characteristics of any given vehicle that is to be used for racing or any other situation in which a premium is placed on performance is to increase the stiffness of its suspension components. The reason for this is that the stiffer suspension will flex less under a load which has the effect of keeping the suspended drive or steering components of the vehicle in contact with the surface over which the vehicle is traveling. A stiffer suspension also lessens the amount of roll (a horizontal change in attitude) of the body of the vehicle in relation to its drive and steering components as it is driven over rough terrain and through corners. A lesser amount of body roll allows an operator to travel faster through corners and over rough terrain because it keeps the weight of the vehicle""s body and operator centered over its drive and steering components which provides more traction and steering impetus to the vehicle in these conditions. Therefore, as a general rule in high performance vehicles, the stiffer that the suspension can be set up, the faster the vehicle will be able to travel over a given set of course obstacles or configurations.
Problems also arise from a vehicle which is set up with a suspension that is too stiff. The first of these is that if the vehicle""s suspension is too stiff the resulting roughness of the ride in difficult terrain will make it impossible for the driver to control the vehicle as he would be bounced around to such a degree that he would be unable to focus on the road or track ahead. Additionally, an extremely stiff suspension would also create problems in the drive and steering mechanisms of a vehicle as they would tend to bounce over surface irregularities and lose contact with the surface over which they are traveling. This loss of surface contact would make the vehicle very difficult to control and, thus, force the vehicle to be driven at a slower rate of speed in order to maintain control over it. Therefore, finding the proper balance between suspension stiffness and controllability is critical to the performance of all types of racing and high performance vehicles.
The stiffness and controllability of the rear suspension of a snowmobile is controlled by the use of a pair of coiled springs that have a spring arm which angles downward and are fixedly attached to a lower suspension component. It is the flexing of the spring arm which primarily facilitates and controls the vertical movement of the suspension as a whole as the snowmobile travels over uneven terrain. The problem with this design is that the only way the spring rate can be varied to either stiffen or soften the suspension to compensate for different terrain conditions is to change out the springs themselves. This is a very time consuming operation which requires that the entire rear suspension assembly be unassembled, resulting in a lot of down time. Therefore, it is desirable to provide a method of varying the stiffness of the rear suspension of a snowmobile without the need of replacing the suspension springs.
It is the primary objective of the present invention to provide a method of stiffening the rear suspension of a typical snowmobile that can be used in conjunction with the original components of the rear suspension.
It is an additional objective of the present invention to provide such a method of stiffening the rear suspension of a snowmobile that provides a greater degree of resistance corresponding to the occurrence of a higher degree of force being placed on the snowmobile.
It is still a further objective of the present invention to provide such a method of stiffening the rear suspension of a snowmobile that works equally effectively with a wide variety of makes and models and that is inexpensive to construct and to sell.
These objectives are accomplished by the use of a cambered surfaced tensioning block that engages the forward portion of the spring arm component of the rear suspension of a snowmobile when sufficient lateral force is applied to the suspension. The spring arms pass through an open ended block housing just above the upper surface of the tensioning block. The tensioning block fits within an open ended block housing which is attached to the slide rail components of the rear suspension in a position that is just rearward of the point at which the spring arms are attached.
The spring arm functions within the rear suspension by flexing downwards and upwards when lateral forces are applied to the snowmobile and serves to both contain these forces and to maintain the suspension in a neutral position during normal operation. This flexing of the spring arm generally occurs within the relatively short portion of the arm that is located directly behind the point of attachment to the slide rail components of the rear suspension. The positioning of the flex or load point of the spring arm creates a relatively soft spring action as the application of force to it is at the furthest possible point from the flex or load point.
The use of the present invention effectively moves the flex or load point of the spring arm rearward and closer to the point at which the force is applied. This is accomplished because as the spring arm begins to flex downward, it contacts the upper surface of the tensioning block which changes the load point from its original position to that at which it is in contact with the tensioning block. Additionally, the upper surface of the tensioning block is formed in a curve in a manner so that the radius of that curve lessens as you move rearward which creates a cambered surface. The cambered upper surface of the tensioning block is utilized to move the load point closer still to the point of force application as the lateral force applied to the suspension increases. Therefore, the use of the present invention provides a rear suspension spring characteristic that grows increasingly stiff as more and more lateral force is applied to it. This improves the handling of snowmobiles in rough terrain which is very desirable in high performance machines.
For a better understanding of the present invention reference should be made to the drawings and the description in which there are illustrated and described preferred embodiments of the present invention.